Physiology Of The Thyroid Gland

Question 1

Give four functions of thyroid hormone

Answer 1

Growth
Metabolism
Normal brain function in adults
Myelation of fibres

Question 2

What is the 1st endocrine gland to develop in embryo

Answer 2

Thyroid gland

Question 3

Describe the structure of the thyroid gland

Answer 3

Made up of two lobes, the left and right lobes and an isthmus in the middle, lies over the trachea.

Question 4

Two functions of thyroid gland

Answer 4

Production of thyroid hormones
Organification of Iodine

Question 5

Name three types of thyroid hormones, and the differences with each other.

Answer 5

1. Thyroxine ( tetraiodothyronine) - T4
   - Has 4 iodine molecules per hormone, is the most abundant form of thyroid hormone in plasma.
2. Tri-iodothyronine- T3
   - Has 3 iodine molecules per hormone, is the most active/ potent form of the thyroid hormones.
3. (Thyro) calcitonin- concerned with calcium metabolism.

Question 6

Explain the process of organification of iodine(3)

Answer 6

1. Follicular cells synthesise the thyroglobulin and enzymes of the colloid.
2. The sodium iodine symporter brings iodine inside the cells. The pendrin transporter transports iodine into the colloid.
3. Enzymes in the colloid add iodine to tyrosine creating T3 and T4.
4. Thyroglobulin leaves the colloid in a vesicle.
5. Intracellular enzymes separate T4 and T3 from the protein.
6. Free T3 and T4 enter circulation.

Question 7

Name the enzyme responsible for the organification of iodine

Answer 7

Thyroperoxidase

Question 8

What affect the release of thyroid hormones(1)

Answer 8

Tonic release

Question 9

Clinical features of congenital hypothyroidism

Answer 9

Prolonged jaundice
Goitre
Failure to gain weight
Dry skin, hair

Question 10

What are the symptoms of hypothyroidism (3)

Answer 10

Dry skin
Hair loss
Weight gain with poor appetite
Feeling cold
Constipation
Poor concentration and memory

Question 11

What are the signs of hypothyroidism (4)

Answer 11

Dry skin
Puffy face
Bradycardia
Carpal tunnel syndrome

Question 12

What are the primary causes of hypothyroidism (3)

Answer 12

Autoimmune hypothyroidism (eg. Hashimoto’s thyroiditis)
Iatrogenic
Drugs
Infiltrative disorders
Congenital
Iodine deficiency

Question 13

What are the secondary causes of hypothyroidism

Answer 13

Hypopituitarism
Hypothalamic diseases

Question 14

What are the symptoms of hyperthyroidism (3)

Answer 14

Heat intolerance and sweating
Weight loss with increased appetite
Diarrhoea
Polyuria
Palpitations
Loss of libido

Question 15

What are the signs of hyperthyroidism (2)

Answer 15

Tachycardia
Tremour
Goitre
Warm, moist skin